Spectral sensitization of silver halide in photographic compositions is generally accomplished by adsorption of sensitizing dye molecules to the surface of silver halide grains. The dye molecules absorb energy of a certain wavelength and transfer that energy to the silver halide, causing formation of a latent image. The use of dye polymers as sensitizing dyes for silver halide in photographic compositions has been proposed for a number of reasons. For example, U.S. Pat. No. 2,639,282 describes resin cyanine dyes that sensitize silver halide and are not subject to wandering in gelatin layers of photographic elements. U.S. Pat. application Ser. No. 239,864, now U.S. Pat. No. 4,950,587 filed Sept. 2, 1988, in the names of M. R. Roberts. D. C. Tabor, and P. B. Gilman, entitled "J-Aggregating Dye Polymers as Spectral Sensitizers for Silver Halide Photographic Compositions" describes dye polymers that J-aggregate when used to sensitize silver halide.
One problem with the successful use of dye polymers to sensitize silver halide in a wide variety of photographic compositions has been the low aqueous dispersibility of the dye polymers, which has led to difficulty in dispersing the dyes in hydrophilic photographic compositions and to objectionable stain caused by dye polymer retained in the element after processing. It would thus be advantageous to provide a dye polymer for sensitizing silver halide in photographic compositions that did not suffer from these problems.